Explain HashMap Resizing Without Long Pauses

Explain how a hash map works internally. Cover how keys are mapped to buckets, how collisions are handled, and when the table decides to resize.

Follow-up: resizing usually requires allocating a larger bucket array and moving existing entries into it, which can create a noticeable latency spike. Design an approach to cap or smooth that latency while preserving expected constant-time lookups and inserts.